First SACCH is used only on dedicated mode
SDCCH on Idle mode.
If we take sdcch/8, and if we take TS1 of the BCH frequency, then 8 SDCCH will share the same TS (dedicated Channel D0, D1, D2, D3, D4, D5, D6, D7, uplink and downlink),But we don’t have at the same time Dn uplink and Dn downlink
when BTS send for example D0 to the mobileStation m1, after 11 frame BTS will receive D0 from mobile station m1.
But during this 11 Frame the BTS receives SACCH from mobile in Dedicated mode or receives other SDDCH from other mobile in idle mode.
The question is probably why 11 Frame?
11 frames = 4.6ms*11=0.0506s